240 Hazen: Lire History oF SPHAERELLA LACUSTRIS 
3a. These megazooids may return immediately to the resting 
condition 1, by secreting a new thick cell-wall inside the distended 
wall which they possess as zooids, or 
36. The megazooids may come to rest temporarily, not form- 
ing any thick cell-wall. 
4a. These temporarily resting zooids may divide into two or 
four new megazooids which repeat the development of 22, indefi- 
nitely, or 
45. They may form eight, sixteen, thirty-two, or sixty-four (?) 
microzooids which swarm actively inside the mother-cell-wall and 
finally break out. 
5a. These microzooids frequently die. 
54. Sometimes they come to rest, form a cell-wall and increase 
to the size of ordinary resting-cells. 
IH. THE Cycre or Microzooips 
Certain resting-cells (probably poorly nourished) form instead 
of megazooids, eight, sixteen, thirty-two, or sixty-four (?) micro- 
zooids which die or conjugate (?) or grow into the ordinary resting- 
cells, 
B. General Conclusions 
I. There are two forms of motile cells produced by Sphaerella 
lacustris : megazooids and microzooids. 
The megazooids are asexual. 
3. No conjugation of microzooids has been observed, but 
from the conditions of their formation we should expect to find 
such a process. 
4. The vegetative division does not differ i in manner from the 
formation of megazooids ; unfavorable conditions prevent the as- 
sumption of the motile state. 
5. Sphaerella lacustris does not pass into an amoeboid form. 
6. The cell-wall both in motile and resting conditions consists 
of cellulose. 
7. Several pyrenoids about which starch is deposited are em- 
bedded in the chromatophore. 
8. No contractile vacuole is present. 
9. Haematochrom is a substance closely allied to chlorophyl 
